Any time a scientific theory is challenged it means it's not a good theory. why?

If a theory is challenged, then that means that the theory may have a specific flaw, making it "not good"

All I know is that a theory is a hypothesis that has been proven correct many times. So based on that if it is a scientific theory that has been proven correct many time by many people and now it is being challenged because maybe something new was discovered. That doesn't always mean it is not a good theory.

Hope this helps.